1. Field of the Invention
The present invention is directed to a process ESD protection device for use during processing with structures containing antifuses. According to this invention, an ESD protection device is formed as close in time as possible to the formation of the antifuse material layer so that the antifuse devices can be protected from ESD occurring during processing.
2. The Prior Art
Metal-to-metal, metal-to-poly (polysilicon), and poly-to-poly antifuses have become increasingly important in one-time user programmable memory and logic devices. However, making metal-to-metal antifuses in high volume production has not been achieved due to various manufacturability concerns. During the fabrication process used for manufacturing antifuse elements, the wafer is exposed to environments which are potentially harmful to the antifuse material positioned between the lower and upper antifuse electrodes. For example, reactive ion plasma etching techniques employed to define small geometry features can result in the accumulation of large static charges giving rise to high voltages across sensitive areas in the integrated circuit being fabricated.
Antifuse materials which are engineered to rupture at predictable (and often relatively low) voltages are very sensitive to this phenomenon. The static charge buildup occurring during processing can easily damage the antifuse device and alter its electrical characteristics without any predictability. The resulting damaged antifuse device will therefore have unpredictable characteristics both with respect to breakdown voltage and with respect to long term stability in either the "on" (conducting) or "off" (non-conducting) states.